Combination process for catalytic hydrodesulfurization and reforming of high sulfur hydrocarbon mixtures



Nov. 6, 1956 LE ROI E. HUTCHINGS EI'AL' COMBINATION PROCESS FORCATALYTIC HYDRODESULFURIZATION AND REFORMING OF HIGH SULFUR HYDROCARBONMIXTURES Filed June 5, 1953 2 Sheets-Sheet l CRUDE OIL FRAGTIONAT/ONVIRGIN NAPh'Tl-IA 0A TALYTIO REFORM/N6 VIRGIN 6A5 OIL I11'YDRODESULFURIZAT'IOIV STAB/LIZER RE FORMED IVA Pl-lTl-IA BYPRODUOTGAS SEPARATDR HYDROGEN SUL F/DE4 H YDRIOGEIV v r v STAB/LIZER h YDRODESULF UR/ZE D l-l YDROGE/VA 7' ION FnAcr/on/A T/OIV LIGHT NAPHTHA VKEROSENE DIESEL FUEL DIESEL FUEL BLEND/N6 STOCK IN VEN TOR.

LERO/ EHUTOH/NGS BY MILTON M. MAR/5V6 A TTORNEY 'Nov- 6, 1956 LE ROI E.HUTCHINGS ETAL v 2,769,753

COMBINATION PROCESS FOR CATALYTIC HYDRQDESULFURIZATION AND REFORMING OFHIGH SULFUR HYDROCARBON MIXTURES Filed June 3, 1955 2 Sheets-Sheet 2FIG. 2

IN VEN TOR.

LE R O! E. HUTOHl/VGS BY MILTON MMAR/S/G A TTOR/VEY United States PatentCOMBINATION PROCESS FOR CATALYTIC HY- DRODESULFURIZATION AND REFORMINGOF HIGH SULFUR HYDROCARBON MIXTURES Le Roi E. Hutchings, Crystal Lake,and Milton M. Marisic, Elgin, 11L, assignors to The Pure Oil Company,Chicago, 111., a corporation of Ohio Application June 3, 1953, SerialNo. 359,268

9 Claims. (Cl. 196-24) The present invention relates to a combinationprocess of catalytic hydrodesulfurization and reforming of high sulfurhydrocarbon mixtures and, more particularly, a method of treating high.sulfur and high aromatic stocks to produce reformed naphtha blendingstock, lowaromatic content kerosene and low-sulfur, high octane numberdiesel fuel. The results herein are obtained by employing an integratedprocess of reforming, hydrodesulfurization, and hydrogenation incombination.

The primary object of the invention is to provide a process of producinggood quality reformed naphtha, low aromatic kerosene and low sulfur,high cetane number diesel fuel from high sulfur, highly aromatichydrocarbon mixtures, and crude oils.

Another object is to provide a combination process of reforming,hydrodesulfurization, and hydrogenation to produce good quality productsfrom high sulfur hydrocarbons.

Another object of the invention is to provide an integrated reforming,hydrodesulfurization, and hydrogenation process to accomplish resultsnot attainable by either process alone.

Still another object of the invention is to provide a combination ofrelated catalytic processes which makes possible the adjustment of theseverity of one process to the advantage and completeness of the others.

And another object of the invention is to provide a combination processinvolving the substantial over-all production of hydrogen to accomplishmore complete desulfurization and dearomatization to the enhancement ofthe individual processes and products therefrom.

These and other objects will become apparent as the description thereofproceeds;

In the drawings, Figure 1 is a schematic flow diagram illustrating thegeneric embodiments of the invention, the relationship of the processesto each other, and to the products produced therefrom.

Figure 2 is a flow diagram illustrating a particular method andapparatus for carrying out the present invention.

In the prior art methods of treating high sulfur crudes to producedesirable products, it has generally been the practice to fractionatethe crude to produce naphtha fractions, kerosene fractions, diesel fuelfractions, and bottoms. The naphtha fractions are subjected to thermalor catalytic reforming to produce gasoline fractions. The kerosenefractions from such crudes, because of their high sulfur content, mustbe subjected to severe desulfurization processes as, for example,extraction with sulfur dioxide. These fractions also contain a highcontent of aromatic type hydrocarbons which are lost in the extractionprocess. This loss in aromatics is reflected in a reduction in totalyield of kerosene produced from a given amount of crude. Furthermore,the diesel fuel fractions are subjected to separate treatment toincrease their cetane number, which may include extraction with sulfurdioxide or the equivalent and thereby further reduce the hydrocarbonsavailable ice as end products. The present integrated three-step processprovides a means for overcoming this loss in yield, and allowing the useof wider fractions of the crude to produce the gasoline blending stocks,kerosenes, and diesel fuel fractions, all having the desirable motorfuel properties, cetane number requirements, and low sulfur contentalong with decreased aromaticity in the kerosen-e fractions, without thenecessity of further treatment of the individual products. By takingrather wide boiling range fractions of the crude, reforming the lighterfraction rather severely for octane number enhancement, and to formhydrogen for recycling to the hydrodesulfurization and hydrogenationreactions without purification other than removal of hydrogen sulfide,these advantages are further realized and the cost, time, and materialsavings are increased. Thus, the sulfur and aromatic hydrocarbons thatare normally lost by the extraction methods currently in use areconverted to new products of increased cetane number, low sulfurcontent, and improved motor fuel characteristics.

In carrying out the present invention, the hydrocarbon mixture is firstfractionated into a naphtha charge stock having a boiling range fromabout 200 to 400 F. and a heavy fraction having a boiling range fromabout 350 to 750 F. The light and heavy fractions may come from onecrude source or from different crude sources. The naphtha charge stockis preheated by indirect contact with products from the reformingoperation and subjected to reforming conditions by first vaporizingunder pressure, mixing with hydrogen which has been preheated, and thenpassing the mixture into the catalytic reforming reactor. The hydrogenis preferably preheated to a higher temperature than the naphtha so thatthe temperature of the mixture is between about 900" and 1100 F. andpreferably about 1000 F. This is accomplished by conducting the hydrogenthrough the hotter portions of the preheating furnace and the naphthathrough the cooler portions of the furnace. The conditions of reformingare adjusted to produce at least the amount of hydrogen that will beneeded for the subsequent hydrodesulfurization and hydrogenationreactions. The conditions used during'reforming will consequently dependon the naphthenicity and aromaticity of the crudes or hydrocarbonmixtures to be treated or from which the charge stocks are derived.

The reforming reaction is carried out in accordance with knownprocedures. By reforming in accordance with this invention is meant aprocess of treating a stock at any elevated temperature in the presenceof a catalyst capable of promoting dehydrogenation and/or aromatizationreactions whereby the straight chain hydrocarbons are aromatized and thenaphthenes are dehydrogenated. The reforming process may or may not becarried on in the presence of added hydrogen. There should be a netover-all production of hydrogen during the process which will depend onthe conditions used and the type of feed hydrocarbons being treated.

For purposes of this invention, any reforming catalyst may be used. Forexample, catalysts of the metal oxide or gel type may be used, as anoxide of a metal of the fifth and sixth periodic groups along withrefractory metal oxides. A gel type catalyst which is suitable for thereaction comprises 18 to 30 mol percent of chromium oxide and from 82 to70 mol percent of aluminum oxide, calculated as CI203 and A1203,respectively. Another suitable catalyst is one containing 10 percent byweight of M003 and percent activated alumina or alumina gel. From 5 to50 mol percent of a metal oxide aromatizing catalyst may be used 'withthe balance being a refractory oxide, such as alumina or the equivalent.The pressure during the reforming reaction may range from 25 to 500pounds per square inch gauge or higher and the flow rate of reactantsthrough the catalyst bed may be 0.1 to liquid volumes of hydrocarbon pervolume of catalyst per hour. The temperature conditions may vary from800 to 1200 F. as long as the hydrocarbons are in the vapor phase underthe conditions imposed.

The preheated'hydrogen and hydrocarbons are thoroughly mixed beforecontacting the reforming catalyst. Since the net reactions areendothermic, there is experineed a fall in temperature in the reactionzone, part of which may be compensated for by preheating the reactantsto a higher temperature than reaction temperature. Even under optimumconditions, the catalyst gradually becomes fouled making regenerationnecessary.

This is accomplished by passing an oxidizing atmosphere through thecatalyst at elevated temperatures, preferably at or above reactiontemperature. i reactors may be used so that one or more may be under- Inpractice, several going a regeneration cycle while the others are onstream. The reformed naphtha or reformed products are next stabilized toremove by-product gases including any hydrogen sulfide formed during thereaction. Stabilization is accomplished by cooling the reformed naphthato ambient temperature whereby the by-product gaseous hydrocarbons andhydrogen sulfide are separated. The hydrogen sulfide may be separatedfrom the by-product gases by alkali wash or treatment with an amineextractant as in a Girbitol unit, followed by desorption or stripping ofthe hydrogen sulfide from the amine solution.

The recovered hydrogen sulfide is ready for use in preparing sulfurcompounds or conversion to free sulfur.

The purified by-product gases may be used as such or they may becontacted with absorber oil in a suitable tower to concentrate thehydrogen. In either case, the hydrogencontaining gas is next compressedto reaction pressure and is ready for recycle back to the reformingoperation or to subsequent processing operations.

The reformed naphtha is passed to a distillation unit where a smallamount of high boiling aromatic material,

polymers, etc., are removed under atmospheric pressure. The product is areformed naphtha gasoline blending stock.

The virgin gas oil having a boiling range of about 350 to 750 F.,separated from the hydrocarbon mixture or from a separate source issubjected to hydrodesulfurization. The hydrodesulfurization reaction iscarried out in the presence of a hydrodesulfurizing catalyst and addedhydrogen at elevated temperatures. In this process, the

sulfur compounds in the charge .stock are converted into hydrogensulfide by the action of hydrogen and desulfurization catalysts, such asmolybdates, sulfides, and oxides of iron group metals and mixturesincluding, for example,

. cobalt molybdate, chromic oxide, vanadium oxide with molybdena andalumina, and sulfides of tungsten, chro mium, or uranium. The hydrogensulfide thus formed is adsorbed by the catalyst and partially orcompletely reacts with the catalyst to form metallic sulfides. Dependingupon the sulfur content of the charge stock, the complete adsorption ofhydrogen sulfide by the catalyst continues for one to six hours or foreven longer periods of time. The process may be discontinued forregeneration of the catalyst as soon as hydrogen sulfide is evidenced inthe product stream. This procedure permits direct use of the hydrogensulfide-free product gases for recycle purposes. The preferred method ofdesulfurization -involves continuing the operation even after hydrogensulfide appears in the product gases. In this case, the

hydrogen sulfide is removed from the product gases by absorption inethanolamine or in other suitable solvents.

-The hydrodesulfurization may be conducted in this manner for many weeksor even months before it is necessary to regenerate the catalyst byoxidation of the carbonaceous deposit. The latter method is preferredfor the present purpose; however, it will be understood from the following description that either method may be used.

Although any hydrodesulfurizing catalyst may be used, it is preferred touse a cobalt oxide-molybdena-alumina catalyst or acopper-molybdena-alumina catalyst. The process may be carried out ineither the liquid or gaseous phase, or mixtures thereof. Thetemperatures may range from 500 to 800 F. and the pressure from 20 to1000 pounds per square inch. The gas oil stock or heavy naphtha fractionsubmitted to this step of the present combination process may containfrom 1 to about 7 percent by weight of sulfur existing in the form ofvarious organic sulfur compounds. The charge may be introduced to thecatalyst at from 0.5 to 10 liquid volumes per bulk volume of catalystper hour.

The third step of the present process includes a hydrogenation step andis applied to the hydrodesulfurized product only. The hydrogenation isdesigned to reduce the aromaticity and unsaturation. The hydrogenationreaction is conducted under hydrogenation conditions with the knownhydrogenation catalysts. Desulfurization may be accomplished during thislast step to some extent but the principal reactions are hydrogenationof the aromatics and polynuclear ring or straight chain hydrocarbonsthat are present. The degree of hydrogenation will depend on theconditions employed. The temperatures used during the hydrogenation stepmay range from 300 to 700 F. with pressures from 500 to 3500 pounds persquare inch. The hydrogen flow rate may vary from 500 to 6000 cubic feetof hydrogen per barrel of hydrodesulfurized naphtha. Sufficientresidence time should be provided to allow almost complete hydrogenationof the heavy naphtha for best results.

A common recycle system for the hydrogen from all three steps ismaintained in accordance with the present invention as shown inFigure 1. The excess hydrogen from the hydrogenation reaction isseparated by stabilization and may be recycled back to the hydrogenationreaction or to the reforming and hydrodesulfurization reactions. Also,the hydrogen separated from the reformed products and thehydrodesulfurized products is recycled to one or the other of thesereactions or is available for the hydrogenation reaction. Hydrogenseparated from the hydrogenated products is recycled back to thehydrogenation reaction without purification.

The process may be illustrated by reference to Figure 2 showing in moredetail the flow relationship of the reactants and products. The naphthacharge from the fractionation unit enters at line 1 propelled by pump 2,passes through heat exchanger 3 via line 4 into coil 5 of furnace 6. Thepreheated naphtha is mixed with recirculated hydrogen (the source ofwhich will be described) from line 7 and passes to head reformer 8.Products from the initial reforming are conducted through line 9 intocoil 10 of furnace 6 for reheating in order to complete the reformingreactions because the reactions taking place in reformer 8 areendothermic and the temperature declines. The reheated partiallyreformed products pass from coil 10 into line 11 and thence to tailreformer 12. In practice, four reformer reactors may be used so that aregeneration cycle may be utilized and the entire reaction madecontinuous. Two reforming reactors maybe on stream while the other twoare undergoing regeneration. Coil 32 of furnace 6 is used to preheat therecirculated hydrogen.

It has been found that the conditions of reforming are fixed by theamount of hydrogen that must be produced for the balance of theprocesses. Also, it is advantageous to preheat the recirculated hydrogento a temperature which is much higher than the naphtha charge enteringthe reformer. The arrangement of coils 5, 10, and 32 in furnace 6 withinprogressively hotter positions in the furnace makes this possible. Thehydrogen being in the lower and hotter coil 32 and the partiallyreformed products being in coil 10 reduce the heat imparted to coil 5 tothe point that the control of the preheating of the naphtha chargetherein to avoid substantial cracking is facilitated. The temperature ofthe mixture of charge naphtha and hydrogen entering reformer 8 is about1000 F.

The reformed products pass from tail reformer 12 via line 13 into heatexchanger 3 to preheat the incoming charge naphtha and pass intostabilizer 14 at about 300 F. under about 250 p. s. i. g. In stabilizer14 the pressure is reduced to release the hydrogen and hydrogen sulfidealong with any fixed gases which pass via line 15 into condenser 16. Anyliquefiable products are returned by line 17. To separate the hydrogenfrom the hydrogen sulfide and any fixed gas, the vapors at about 100 F.and 240 p. s. i. g. issuing from condenser 16 are passed via line 18,heat exchanger 19, line 20 into the bottom of the first stage of aGirbitol unit.

In the first stage absorber 21 the gases are passed in countercurrentcontact with an amine solution or the equivalent which is recirculatedby pump 22 via line 23 to the top of the unit. The amine solution Washesout the hydrogen sulfide and the spent solution passes via line 24, heatexchanger 25, and line 26 to second stage desorber 27 of the Girbitolunit. In desorber 27 the pressure is reduced to atmospheric and thehydrogen sulfide released from the amine solution by the application ofheat. The released hydrogen sulfide is drawn off at line 28 and may beconverted to free sulfur.

The purified hydrogen passes overhead from absorber 21 via line 29through heat exchanger 19, where it cools the vapors from stabilizer 14,and then it is compressed in compressor 30 to about 250 p. s. i. g.,pumped through line 31 for preheating in coil 32, as previouslydescribed, to complete the hydrogen recycle for the reforming step. Thereformed products from stabilizer 14 pass through line 33 tofractionator 34 where a small amount of high boiling aromatic material,polymers, etc., are separated at 35 and a reformed naphtha gasoline istaken ofi as overhead at 36.

The second stage of the process, comprising the hydrodesulfurization andhydrogenation reactions, is conducted by introducing the heavy naphthaat line propelled by pump 41 through heat exchanger 42, line 43, intocoil 44 of furnace 45. In the arrangement shown, one Girbitol unit isused to separate and purify the hydrogen present in the reformedproducts and in the hydrodesulfurization products. Separate Girbitolunits may be employed if necessary. Purified hydrogen from the combinedoutput of the Girbitol unit may be used for treating the heavy naphtha.For this purpose, a part of the hydrogen from compressor 30 is divertedover line 46 to preheating coil 47 of furnace 45. Preheated heavynaphtha at about 375 to 700 F. passes from coil 44 into line 43 to meetthe preheated hydrogen at 700 F. from coil 47 and line 50 and themixture passes at about 250 p. s. i. g. into either reactor 5?. or 52for hydrodesulfurization. One of the hydrodesulfurization reactors maybe on stream while the other is undergoing regeneration. Thedesulfurized products pass by line 53, heat exchanger 54, line 55, heatexchanger 42, into stabilizer 56. In heat exchanger 42, the incomingheavy naphtha is preheated by the hot desulfurized products. Instabilizer 56, which functions like stabilizer 14, the hydrogen andhydrogen sulfide are separated, and sent by lines 57 and 58 through heatexchanger 19 to the Girbitol unit 21. The products from stabilizer 56pass through heat exchanger 54, line 60, compressor 61, and mix withrecycle hydrogen from line 46 after it has been compressed by compressor62. The mixture passes via lines 63 and 64 to hydrogenation unit 65. Therecycle hydrogen is used in the hydrogenation without furtherpurification. The mixture entering the hydrogenation unit 65 ismaintained at about 425 F. under 3000 p. s. i. g. with about 5000 cubicfeet of hydrogen, as measured under standard conditions, per barrel ofdesulfurized naphtha. Sufficient residence time in the hydrogenationunit is maintained to provide for substantially 6 complete hydrogenationof the heavy naphtha and light gas oil.

The hydrogenated product from unit passes through line 66 to stabilizer67. The separated hydrogen is recompressed by compressor 68 and returnedto the reaction, again without further purification. The resultant heavynaphtha product from stabilizer 67 passes through line 70' tofractionator 71, operated under atmospheric pressure, wherein a lightnaphtha fraction is removed at 72, through the use of reflux condenser73. Similarly, a kerosene and No. 1 diesel fuel are removed by strippingtower 74 and collected at 75 while light ends are returned via line 76;and a diesel fuel blending stock is taken off by means of a secondstripping tower 77 and collected at 78. The bottoms fraction is removedat 79.

The flow system just described necessarily omits mention of theappropriate accessory equipment and control equipment commonly known inthe art, for the sake of brevity. In addition the necessary equipment toaccomplish the regeneration steps has been omitted, such means beingwell known and not a part of this invention.

In order to further demonstrate the invention, the following specificexample is given. A high sulfur crude is fractionated to give a lightvirgin naphtha and a heavy naphtha, a gas oil and bottoms fractions. Theproperties of the crude and the distillation products therefrom areshown in Table I. The crude oil used was a Worland crude from the Stateof Wyoming.

TABLE I Charge properties Yield Aro- Naph- Paraf- Fraction Percent S,wt. API matics, thenes, fins, Vol. Percent Gravity Vol. Vol. Vol.

Percent Percent Percent 39. 0 .30 56. 2 15 38 47 24.7 1.01 38.1 26 01123.5 2. S2 580 F. Flash bottoms 11.0 3. 76 I 1 ASIM Motor Method OctaneNumber, 51.7. 2 Splits into 12.4% kerosene (S-0.81%), 12.4% Diesel Fuel(S1.21%, octane number, 40).

Considering a crude capacity of 10,000 bbls./ day, the gasoline or lightnaphtha cut will comprise 3,900 bbls./ day to be sent to the reformers 8and 12 (Figure 2) and the heavy naphtha fraction (400600 F.) willcomprise about 2,470 bbls./day which will yield approximately 1,220bbls./ day each of desulfurized and hydrogenated kerosene and dieselfuel. The reforming reaction was carried out at about 960 F. During thereforming operation, the naphthenes and some of the paraffinhydrocarbons are converted to aromatics and the sulfur compounds arereduced to the corresponding hydrocarbons and hydrogen sulfide. Theproducts and material balance from this operation are shown in Table II.

TABLE II 1 Hz to hydrogcnate olefins produced by cracking S compoundsand to produce HzS.

The heavy naphtha charge enters the process through line 40 and issubjected to hydrodesulfurization in reactors 51 and 52 maintained atabout 800 F. in the presence of all or a portion of the hydrogen fromthe reforming step. During this reaction little or no dehydrogenationoccurs and the predominant portion of the olefins produced resultingfrom cracking of the sulfur compounds are hydrogenated duringhydrodesulfurization.

lyst. The hydrogenation proceeds under conditions such that the contentof aromatics in the feed is converted to the corresponding saturatedcompounds, thus reducing the aromaticity of the kerosene fractiontherein while at the .same time effecting little or no desulfurizationor transformation of the other hydrocarbons present. The recycle ofhydrogen from this operation without subsequent purification has beenfound to facilitate this result to give kerosene fractions of goodburning quality and diesel fuel blending stocks having high cetanenumbers. The hydrogenated products are distilled for separation of lightand heavy fractions and blending stocks for kerosenes and diesel fuels.Table III presents the properties and material balance of the productsof this combined hydrodesulfurization-hydrogenation process.

TABLE III Hydrodesulfurization-hydrogenation operation Consumption o 2Percent Percent Bbls./ Cetane Fraction Aro- Sulfur day No.

matics 1,000 cf Lbs./

S.c.e.d. day as S Charge 26 1. 01 2, 470 B 80 7, 200 (40) (400600F.) 3.03 2, 490 2, 280 220 Kerosene 2 02 1, 220 91 65 Diesel Fuel 4 .04 1,220 l, 280 145 52 Light Naphtha. 1 .01 25 3O 2 Heavy Oil 5 60 8 HzS Z 807, 070 Excess H2 1, 738

Tails from kerosene and diesel fuel production. Not essential tooperation.

2 Hz to produce H28 and hydrcgenate olefins.

Since the distillation ranges of kerosene and diesel fuel overlapblending must be used to allow continuous production of both of theseproducts. It is particularly pointed out that the production of keroseneand diesel fuel nearly equals the amount of material charged to theprocwith this invention comprise any mixture of hydrocarbons regardlessof source or chemical constitution which have a high content of sulfuror sulfur compounds. Such hydrol carbon mixtures generally havecorrespondingly high aromatic hydrocarbon contents and as such areextremely difficult to treat for the purpose of producing good fuels,naphthas, and kerosenes. The sulfur may be present as elemental sulfurbut is generally present as sulfur compounds including hydrogen sulfide,organic sulfides, and disulfides of aromatic, naphthenic, and polycyclicorigin.

By high sulfur content is meant those mixtures including .crude oilshaving from 1.0 to 3.0 weight percent of sulfur present. Also includedare those mixtures having as high as 5.0 percent of sulfur. Such crudeoils or mixtures may have an API gravity ranging from about 20 to 40.

The lighter fractions separated for treatment in accordance with thisinvention will naturally contain lesser amounts of total sulfur as aresult of fractionation. The light fraction which will boil above about200 P. will have a sulfur content of about 0.1 to 0.4 weight percentalthough this amount may be above or below this figure. Likewise, theheavy fraction boiling above about 350 F. will have 1.0 percent or moreof sulfur. The volume percent of aromatics, naphthenes, and paraffinspresent in these fractions may vary somewhat from that described inTable I, depending on the source of the crude oil.

An advantage of the present invention is that, by the employment of acommon recycle system between the three integrated reactions, theconditions of reforming may be adjusted and maintained to continuouslyproduce good blending naphtha while at the same time, because of theseverity of reforming, produce suificient recycle hydrogen to be used inboth the hydrodesulfurization reaction and the hydrogenation reaction.

What is claimed is:

1. The process for improving the motor fuel characteristics anddecreasing the sulfur content and aromaticity of fractions obtained fromhigh sulfur content hydrocarbon mixtures which comprises separating saidhydrocarbon mixtures into a light fraction having an initial boilingpoint of about 200 F. and a heavy fraction having an initial boilingpoint of about 350 F., subjecting said light fraction to catalyticreforming and separating a reformed naphtha blending stock, subjectingsaid heavy fraction to hydrodesulfurization to produce ahydrodesulfurized product, subjecting said hydrodesulfurized product tohydrogenation at about 300 to 700 F. under conditions to dearomatizesame and fractionating the hydrogenated product so produced to yieldfractions of improved cetane number and low aromatic content.

2. The process in accordance with claim 1 in which said hydrogenation iscarried out at about 300 to 700 F. in the presence of a catalystselected from the group consisting of nickel and nickel oxide.

3. Process for improving the motor fuel characteristics and decreasingthe sulfur content and aromaticity of fractions obtained from highsulfur content hydrocarbon mixtures which comprises separating saidhydrocarbon mixtures into a light fraction boiling between about 200 to400 F. and a heavy fraction boiling between about 350 to 750 F.,subjecting said light fraction to catalytic reforming and separating areformed naphtha blending stock and a hydrogen-rich fraction therefrom,subjecting said heavy fraction to hydrodesulfurization in the presenceof said hydrogen-rich fraction and separating a hydrodesulfurizedproduct and a second hydrogen-rich fraction therefrom, subjecting saidhydrodesulfurized product to hydrogenation at about 300 to 700 F. underconditions to dearomatize same in the presence of at least a portion ofsaid hydrogen-rich fractions and fractionating the hydrogenated productsso produced to yield a light naphtha, a diesel fuel fraction having goodengine fuel characteristics and improved cetane number, and a kerosenefraction of low aromatic content.

4. The process in accordance with claim 3 in which the hydrocarbonmixture being treated comprises a crude oil having a total sulfurcontent of at least about 1.00 weight percent.

5. The process in accordance with claim 4 in which the hydrocarbonmixture is a Worland crude having a total sulfur content of about 1.70weight percent.

6. The process in accordance with claim 3 in which the hydrocarbonmixture is a high sulfur crude having an API gravity of about 37.9.

7. The process in accordance with claim 1 in which said hydrogenation isconducted at a temperature of about 550 F. in the presence of a catalystselected from the group consisting of nickel and nickel oxide.

8. A process for improving the diesel fuel characteristics anddecreasing the sulfur content and aromaticity of fractions obtained froma crude oil containing at least about 1.0 percent by weight of sulphurcomprising fractionating said crude oil to obtain a light fractionboiling between about 200 to 400 F. and a heavy fraction boiling betweenabout 350 to 750 F., subjecting said light fraction to reforming undersevere conditions at a temperature of about 900 to 1100 F. in thepresence of hydrogen and separating a reformed naphtha blending stock,subjecting said heavy naphtha to hydrodesulfurization at a temperaturefrom about 500 to 800 F. and separating a hydrodesulfurized product,subjecting said hydrodesulfurized product to hydrogenation at atemperature of about 300 to 700 F. under dearornatizing conditions, andfractionating the products produced from said hydrogenation to producefractions of improved characteristics.

9. The process of improving the motor fuel characteristics of reformednaphtha, decreasing the sulfur content and aromaticity of light naphthaand kerosene fractions, and increasing the cetane number of diesel fuelfractions obtained from crude hydrocarbon mixtures having a total sulfurcontent of about 1.7 weight percent and an API gravity of about 37.9comprising separating said mixture into a light fraction having aboiling range between about 200 and 400 F. and a heavy fraction having aboiling range between about 350 and 600 F., subjecting said lightfraction to reforming at about 960 F. to produce a reformed naphthahaving a sulfur content of about 0.005 weight percent, subjecting saidheavy fraction to hydrodesulfurization at about 800 F. to produce aproduct having a sulfur content of about 0.15 weight percent andsubjecting said hydrodesulfurized product to hydrogenation at about 300to 700 F. under conditions to dearomatize same and fractionating thehydrogenated product to produce a kerosene fraction having about 0.02percent sulfur by weight and a diesel fuel having a centane number ofabout 52.

References Cited in the tile of this patent UNITED STATES PATENTS2,300,877 Drennan Nov. 3, 1942 2,304,183 Layng Dec. 8, 1942 2,417,308L'ee Mar. 11, 1947 2,419,029 Oberfell Apr. 15, 1947 2,580,478 Stine Jan.1, 1952 2,691,623 Hartley Oct. 12, 1954

1. THE PROCESS FOR IMPROVING THE MOTOR FUEL CHARACTERISTICS ANDDECREASING THE SULFUR CONTENT AND AROMATICITY OF FRACTIONS OBTAINED FROMHIGH SULFUR CONTENT HYDROCARBON MIXTURES WHICH COMPRISES SEPARATING SAIDHYDROCARBON MIXTURES INTO A LIGHT FRACTION HAVING AN INITIAL BOILINGPOINT OF ABOUT 200* F. AND HEAVY FRACTION HAVING AN INITIAL BOILINGPOING OF ABOUT 350* F., SUBJECTING SAID LIGHT FRACTION TO CATALYTICREFORMING AND SEPARATING A REFORMED NAPHTHA BLENDING STOCK, SUBJECTINGSAID HEAVY FRAACTION TO HYDRODESULFURIZATION TO PRODUCE AHYDRODESULFURIZED PRODUCT, SUBJECTING SAID HYDRODESULFURIZED PRODUCT TOHYDROGENATION AT ABOUT 300* TO 700* F. UNDER CONDITIONS TO DEAROMATIZESAME AND FRACTIONATING THE HYDROGENATED PRODUCTS SO PRODUCED TO YIELDFRACTIONS OF IMPROVED CETANE NUMBER AND LOW AROMATIC CONTENT.